caste system in india-genetic basis

A 2001 genetic study, led by Michael Bamshad of University of Utah, found that the genetic affinity of Indians to Europeans is proportionate to caste rank, the upper castes being most similar to Europeans, whereas lower castes are more like Asians. The researchers believe that the Indo-European speakers entered India from the Northwest, admixing with or displacing the proto-Dravidian speakers. Subsequently they may have established a caste system and placed themselves primarily in higher castes. The study concludes that the Indian castes “are most likely to be of proto-Asian origin with West Eurasian admixture resulting in rank-related and sex-specific differences in the genetic affinities of castes to Asians and Europeans.”.[2] Because the Indian samples for this study were taken from a single geographical area, it remains to be investigated whether its findings can be safely generalized.[3]
A 2003 report by T. Kivisild et al. concluded that the “Indian tribal and caste populations derive largely from the same genetic heritage of Pleistocene southern and western Asians and have received limited gene flow from external regions since the Holocene.” These scientists conclude that their observation does not refute the existence of genetic footprints in India from central Asia, eastern Europe or elsewhere. The genetic influence is higher in northwest regions of India, than other parts. Further, such broad estimates, according to these scientists are preliminary, at best. It will take larger sample sizes, more populations, and increased molecular resolution to determine the impact of historic gene flows to India.[4]
A 2006 genetic study by the National Institute of Biologicals in India, testing a sample of men from 32 tribal and 45 caste groups, concluded that the Indians have acquired very few genes from Indo-European speakers.[5] The conclusion of this study has been disputed by later studies.[6]
According to a 2006 study by Ismail Thanseem et al. of Centre for Cellular and Molecular Biology (India) “the vast majority (>98%) of the Indian maternal gene pool, consisting of Indo-European and Dravidian speakers, is genetically more or less uniform”, while the invasions after the late Pleistocene settlement might have been mostly male-mediated.[7] The study concluded that the “lower caste groups might have originated with the hierarchical divisions that arose within the tribal groups with the spread of Neolithic agriculturalists, much earlier than the arrival of Aryan speakers”, and “the Indo-Europeans established themselves as upper castes among this already developed caste-like class structure within the tribes.” The study indicated that the Indian caste system may have its roots much before the arrival of the Indo-Aryan immigrants; a rudimentary version of the caste system may have emerged with the shift towards cultivation and settlements, and the divisions may have become more well-defined and intensified with the arrival of Indo-Aryans.[8]
A 2009 article published in Nature finds strong evidence for at least two ancient populations in India, genetically divergent, that are ancestral to most Indians today. One, the Ancestral North Indians, who are genetically close to Middle Easterners, Central Asians, and Europeans, whereas the other, the Ancestral South Indians, who are genetically distinct from Ancestral North Indians and East Asians as they are from each other. The study observes that genetic markers suggest endogamy within population clusters was prevalent in various Indian kingdoms over time. The report includes a novel method to estimate ancestry without accurate ancestral populations. With this method, the scientists show that Ancestral North Indians ancestry ranges from 39–71% in most Indian groups, and is higher in traditionally upper caste and Indo-European language speakers. Groups with only Ancestral South Indians ancestry may no longer exist in mainland India due to genetic pool mixing. However, the indigenous Andaman Islanders are unique in being Ancestral South Indians-related groups without Ancestral North Indians ancestry.[6][9]
A 2010 review claims that there are at least four population groups in diverse India.[10] Other than Ancestral North Indians and Ancestral South Indians, the population consists of Tibeto-Burman, Austro-Asiatic and Andamanese genetic pools suggesting human beings migrated into India from Africa, Eurasia, Tibet and southeast Asia. The review paper notes that studies so far were based on small sample sets for the diversity in India. With the availability of new genotyping technologies, future diversity studies encompassing a large number of populations, both tribals and castes, at the genome-wide level may help understand patterns of micro-evolution of populations in India. The caste system in India is possibly a complex intra-group and inter-group admix of interactions between various population groups.